<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        * {
            padding: 0;
            margin: 0;
            list-style: none;
        }

        .move-box {
            width: 600px;
            height: 300px;
            margin: 150px auto 0;
            background-color: aquamarine;
            position: relative;
        }

        .ball {
            width: 60px;
            height: 60px;
            background-color: bisque;
            border-radius: 50%;
            position: absolute;
            left: 0;
            top: 50%;
            margin-top: -30px;
        }
    </style>
</head>
<body>
    <div class="move-box">
        <span class="ball"></span>
    </div>
    <script src="move_div.js"></script>
</body>
</html>